The present invention relates generally to the cooling of heat generating surfaces and objects. More specifically, the present invention relates to apparatuses for dissipating heat generated by such objects. In addition, the present invention relates to the use of composite materials in electronic devices to dissipating heat away from heat generating components within the devices and to avoid component failure and failure of the overall device.
In industry, there are various parts and components that generate heat during operation. For example, in the portable electronics industry, it is well known that cellular phones include electronic components that run very hot thus causing a severe overheating problem within the cellular phone itself. Various types of electronic device packages and integrated circuit chips, such as the central processing chip and signal generator chips used in cellular telephones are such devices that generate heat. These integrated circuit devices, particularly the central processing chips, generate a great deal of heat during operation, which must be removed to prevent adverse effects on operation of the system into which the device is installed. For example, a cellular telephone processor chip, which is generally installed into a very compact and densely constructed device, is highly susceptible to overheating which could destroy the processor chip itself or other components proximal to the microprocessor.
There are a number of prior art methods to cool heat generating components and objects to avoid device failure and overheating, as discussed above. A block heat sink or heat spreader is commonly placed into communication with the heat-generating surface of the object to dissipate the heat therefrom. Such a heat sink typically includes a base member with a number of individual cooling members, such as fins, posts or pins, to assist in the dissipation of heat. The geometry of the cooling members is designed to improve the surface area of the heat sink with the ambient air for optimal heat dissipation. The use of such fins, posts of pins in an optimal geometrical configuration greatly enhances heat dissipation compared to devices with no such additional cooling members, such as a flat heat spreader. The drawback to the use of these types of heat dissipation devices is that they necessarily conduct the heat to the outside surface of the device being cooled. In this case the outer surfaces of a cellular telephone can get quite hot, an undesirable result for a hand held electronic device.
To further enhance airflow and resultant heat dissipation, fans and devices have been used, either internally or externally. However, these external devices consume power and have numerous moving parts. As a result, heat sink assemblies with active devices are subject to failure and are much less reliable than a device that is solely passive in nature. In addition, due to the compact nature of a cellular telephone and the limited battery life available to power the electronics, these active device solutions are simply ineffective.
It has been discovered that more efficient cooling of electronics can be obtained through the use of passive devices that require no external power source and contain no moving parts. The devices of the prior art are simply the technology previously used for CPUs and modified to connect to other processing packages. In particular, machined block heat sinks or heat spreader plates of metal have been typically used for cooling cellular processor chips, as described above. Since the prior art heat sink is made of metal, it must be machined to achieve the desired fin configuration. Since the machining process is limited, the geometry of the fin configuration of a machined heat sink is inherently limited.
In the heat sink industries, it has been well known to employ metallic materials for thermal conductivity applications, such as heat dissipation for cooling semiconductor device packages. For these applications, such as heat sinks, the metallic material typically is tooled or machined from bulk metals into the desired configuration. However, such metallic conductive articles are typically very heavy, costly to machine and are susceptible to corrosion. Further, the geometries of machined metallic heat dissipating articles are very limited to the inherent limitations associated with the machining or tooling process. As a result, the requirement of use of metallic materials which are machined into the desired form, place severe limitations on heat sink design particular when it is known that certain geometries, simply by virtue of their design, would realize better efficiency but are not attainable due to the limitations in machining metallic articles.
It is widely known in the prior art that improving the overall geometry of a heat-dissipating article can greatly enhance the overall performance of the article even if the material is the same. Therefore, the need for improved heat sink geometries necessitated an alternative to the machining of bulk metallic materials. To meet this need, attempts have been made in the prior art to provide molded compositions that include conductive filler material therein to provide the necessary thermal conductivity. The ability to mold a conductive composite enabled the design of more complex part geometries to realize improved performance of the part.
In addition, due to the compact size of portable electronics, processor components are typically designed to fit into tight and narrow spaces. However, these components now require heat dissipation for which there is very little or no space.
In view of the foregoing, there is a demand for a heat sink assembly that is capable of dissipating heat. There is a demand for a passive heat sink assembly with no moving parts that can provide heat dissipation without the use of active components. In addition, there is a demand for a complete heat sink assembly that can provide greatly enhanced heat dissipation over prior art passive devices with improved heat sink geometry. There is a demand for a heat sink assembly that can provide heat dissipation in a low profile configuration. There is a further demand for a net-shape molded heat sink assembly that is well suited for cooling processor components within portable electronic devices, such as cellular telephones.
The present invention preserves the advantages of prior art heat dissipation devices, heat exchangers and heat spreaders. In addition, it provides new advantages not found in currently available devices and overcomes many disadvantages of such currently available devices.
The invention is generally directed to the novel and unique composite molded heat exchanger that is net-shape molded of a thermally conductive polymer composition over a heat pipe. The present invention relates to a molded heat exchanger for dissipating heat from a heat-generating source, such as a processor semiconductor chip or electronic components in a portable electronic device, such as a cellular telephone.
The present invention provides for the use of a cellular phone antenna as a heat-dissipating member to remove heat from the cellular phone to avoid overheating. As shown in the attached drawing figures, the invention includes a heat pipe overmolded with a thermally conductive polymer composition. This thermally conductive polymer composition may be easily molded into any desired configuration to which permits the formation of complex geometries to improve the overall thermal dissipation performance of the antenna. The antenna, includes the heat pipe overmolded with a thermally conductive polymer composition, is thermally interconnected to the components of the cellular phone that run hot. As result of the present invention, heat dissipation of thermally conductive components within the cellular phone may be easily carried out to maintain the temperature of the body of the cellular phone itself within an acceptable range.
The molded heat exchanger of the present invention has many advantages over prior art heat sinks in that the heat dissipation element is injection molded from thermally conductive polymer materials which enables the part to be made in complex geometries. These complex geometries enable the heat sink fin configuration to be optimized to be more efficient thus dissipating more heat. As a result, the molded heat exchanger is freely convecting through the part, which makes it more efficient. The ability to injection mold the heat exchanger permits the optimal configuration to be realized and achieved. A heat pipe configuration is provided which extends to the various heat generating components within the device to conduct the heat from the interior of the device to the molded heat sink portion of the present invention. With the present molded he exchanger, the heat sink fins can be designed to what is thermally best while not being limited to the manufacturing and mechanical limitations with prior art processes, such as brazing.
In addition to providing a conduit by which to conduct heat from the various electronic components within the cellular telephone, the metallic construction of the outer casing of the heat pipe also makes it suited to act as an antenna for sending and receiving the RF signal required for the telephone""s functionality. Thus, by placing the heat pipe and overmolded heat sink in the position of a cellular antenna, the heat is conducted to a location not normally contacted by the user during operation of the device, preventing the user from having to hold onto potentially hot surfaces.
It is therefore an object of the present invention to provide a heat-dissipating device that can provide enhanced heat dissipation for a heat generating component or object.
It is an object of the present invention to provide a heat-dissipating device that can provide heat dissipation for semiconductor devices in a portable electronic device, such as a cellular telephone.
It is a further object of the present invention to provide a heat-dissipating device that has no moving parts.
Another object of the present invention is to provide a heat-dissipating device that is completely passive and does not consume power.
A further object of the present invention is to provide a composite heat dissipation device that inexpensive to manufacture.
An object of the present invention is to provide a heat exchanger that is net-shape moldable and has pathway by which to convey heat to a convenient location for dissipation.
Yet another objection of the present invention is to provide a molded exchanger that has a low profile configuration without sacrificing thermal transfer efficiency.